The present invention is derived as an improvement in high capacity evacuation systems employing a first stage jet diffuser and a second stage liquid ring pump for handling fluids having liquid and gaseous phases. It has general application in such systems although it initially arose in consideration of such systems which are used to evacuate corrosive fluids from phosphoric acid evaporators and thus has specific application to evacuation systems which handle corrosive fluids.
In U.S. Pat. No. 3,315,879 there is disclosed an evacuation system capable of handling, at high capacity, fluids having liquid and gaseous phases. In that system, the liquid ring pump forms a second stage to a first stage jet diffuser. A condenser is interposed between the diffuser and liquid ring pump and separates condensable and noncondensable components of an air mixture evacuated from a condenser of a power plant. The condenser or separating means separates out the liquid and directs it to the inlet portion of the liquid ring pump so that only noncondensable fluid components reach the inlet of the jet diffuser. The patented system requires a liquid trap downstream of the separating means and upstream of the suction portion of the liquid ring pump to prevent back flow of separated liquid to the inlet portion of the jet diffuser. The system also requires valving within the system to accommodate hogging and changeover from hogging to the maintenance of high vacuum and further valving is required for recirculation of seal liquid.
Furthermore, the patented system is a "closed" system in which the separated, noncondensable fluid is recirculated to be used as the motivating fluid for the jet diffuser. Also, the closed system provides for recirculating seal liquid. Such a closed system, besides requiring the valving as noted above, also requires cooling apparatus for cooling recirculated seal liquid. Inasmuch as the motivating fluid for the jet diffuser comprises the processed fluid in such a system, corrosive fumes would be recirculated in applications of such a system to corrosive fume producing evacuations.